Disclosed herein are novel polyurethane dispersants and stable aqueous particle dispersions made therefrom, especially pigment dispersions, a process of making the pigment dispersions, and use thereof in ink jet inks.
Polyurethane polymers can be manufactured by a variety of well-known methods, but are often prepared by first making an isocyanate-terminated “pre-polymer” from polyols, polyisocyanates and other optional compounds, then chain-extending and/or chain-terminating this pre-polymer to obtain a polymer possessing an appropriate molecular weight and other properties for a desired end use. Tri- and higher-functional starting components can be utilized to impart some level of branching and/or crosslinking to the polymer structure (as opposed to simple chain extension).
Polyurethane dispersions that are used as pigment dispersants have been described in U.S. Pat. No. 6,133,890. These polyurethanes are prepared with an excess of isocyanate reactive group and are limited to the presence of polyalkylene oxide components. Aqueous polyurethane dispersants have found limited use as dispersants for pigments and the like.
None of the above publications disclose polyurethane dispersions used as pigment dispersants that are derived from water dispersible urea terminated polyurethanes based on certain dials.
There is still a need for polyurethane dispersions which are stable and provide improved performance properties when utilized in desired end uses, such as when utilized as a pigment dispersant in ink jet ink applications. These polyurethanes, as discovered herein, can be used as dispersants for pigments, especially pigments for inkjet inks, and posses a unique balance of properties especially desirable for ink jet ink applications.